Failure of a High Pressure Synthesis Feed Pipe in an Ammonia Plant
The failure of a high pressure hydrogen-based synthetic gas feed line to the ammonia converter produced a sudden explosion followed by a severe fire. One of the operators was fatally injured. The failure of the feed line was characterized by a sudden rupture. There was no leakage prior to rupture. Portions of the piping shattered in a brittle fracture, which was produced due to a severe hydrogen attack. Extensive blisters were observed on the inside surface which failed.The initial crack probably originated at one of two small nozzles provided for temperature measurements. These small nozzles acted as stress raisers.
Event Date
December 9, 1984
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Causes
Cause Comments
The immediate cause was failure of a high pressure synthesis pipe due to internal hydrogen attack, which induced steel decarbonization and brittle fracture. Probably the possibility of the hydrogen attack was not taken into consideration in the design and the maintenance phases.
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
syngas pipeline, ammonia reactor
Storage/Process Medium
Location Type
Location description
Industrial Area
Pre-event Summary
The failed pipe had a diameter of 323.9 mm and a wall thickness of 36 mm .
Number of Fatalities
2
Currency
Lessons Learned
Lessons Learned
Because of the long-term aspects of a failure of the type of this event, in 1986 Prescott et al. (see references) was recommending all operators of ammonia plants to check the alloy content of components and welds, and to check alloys operating limits for in hydrogen service to avoid decarburization and cracking.
Event Nature
Emergency Action
Unknown
Release Type
Release Substance
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Source Category
References
References
Prescott et al., "Failure of High Pressure Synthesis Pipe", Plant/Operations Process, Vol.5 (1986), No.3, pp. 155-l59